For more than 30 years, video inspection has been a baseline fundamental analytical tool for the evaluation and assessment of pipeline integrity. Originally developed as an aid for sewer system maintenance, video inspection equipment and techniques have played a key role in the development of “no-dig” and “trenchless” pipeline rehabilitation methods. This is because the choice of the best trenchless rehabilitation method, for any given application, is often largely based on the video inspection that takes place prior to the rehabilitation. Thus, the information gleaned from the pre-rehabilitation video inspection is used as the basis for key decisions that drive the entire rehabilitation process.
The inspection of pipes often falls into two broad categories: inspections performed for purposes of preventative maintenance, and inspections performed as a response to a need for repair maintenance. The former category may include such things as locating cracks in the pipeline prior to their reaching a critical length, discovering the location of unknown branches or service tees, determining the exact location of valves and fittings, and finding water within the pipeline. In general, video inspection equipment is useful as a proactive tool for assessing the cleanliness, corrosion, and structural integrity of the pipeline. In the case of repair maintenance, high quality video inspection data is also very important. Indeed, the very nature of repair maintenance is such that it may include responding to emergency situations, particularly where hazardous materials are involved. Thus, the importance of quality video inspection equipment and techniques is further underscored.
One attempt to provide a pipe inspection system that can be used in a gas pipeline is described in U.S. Pat. No. 5,195,392 (Moore et al.). Moore et al. describes an inspection system for a pipeline that utilizes a camera head at the end of a snake which is fed down the pipeline to capture images at a desired location. The inspection system of Moore et al. requires two operators: one to feed the snake and camera head down the pipeline, and a second to view the images captured by the camera and provide instructions to the operator moving the camera. The snake is wound around a drum, and uncoiled by the first operator as the camera is manually fed down the pipeline. Moore et al. does note that some commercially available snakes may have electrically powered drum rotation. The camera may be provided with a number of centralizing members which are used to keep the camera approximately centered within the cross-section of the pipeline. After the camera is inserted in the pipeline, a curved tube can be positioned about the snake within the pipeline, and clamped in place.
One limitation of the pipeline inspection system described in Moore et al. is that it requires two operators to perform the inspection task. The first is required to feed the snake and camera down the pipeline, while the second is required to view the images from the camera and direct positioning of the camera by the first operator. In addition, the first operator is required to remain in close proximity to the opening of the pipeline, which may be undesirable if the pipeline is carrying pressurized gas. Although Moore et al. does contemplate the use of a motorized snake drum, an operator is still required to feed the snake down the pipeline under the direction of the second operator. Another limitation of the inspection system described in Moore et al. is that the camera must be placed through an opening in the pipeline prior to the opening being sealed by placement of the curved tube and its associated gasket. Thus, the opening to the pipeline remains unsealed until the camera head and a portion of the snake are inserted. This may be particularly undesirable when inspecting a high-pressure gas pipeline.
Therefore, a need exists for an inspection system that can be used to inspect a high-pressure gas pipeline, and that can be installed under sealed conditions so that seals are in place before the inspection apparatus is inserted into the pipeline. It would also be desirable to have a pipeline inspection system that would allow a single operator to control a camera from a location away from the pipeline opening, particularly where the pipeline is a high-pressure gas pipeline. In addition, it would also be desirable to have a pipeline inspection system with a camera having a positioning system which automatically deploys and retracts upon insertion and retraction of the camera, without the need for manual manipulation of the positioning system by an operator.